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Publication numberUS5828155 A
Publication typeGrant
Application numberUS 08/659,240
Publication dateOct 27, 1998
Filing dateJun 5, 1996
Priority dateDec 8, 1995
Fee statusPaid
Publication number08659240, 659240, US 5828155 A, US 5828155A, US-A-5828155, US5828155 A, US5828155A
InventorsKatsumi Adachi, Kyoko Kurusu
Original AssigneeMitsubishi Denki Kabushiki Kaisha
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Alternating current generator
US 5828155 A
Abstract
An alternating current generator for a vehicle, in which durability is improved, magnetic fluxes are prevented from leaking, and noises are reduced. In the alternating current generator, a ring made of a steel material is disposed so as to abut against field core claws and on the outer peripheral side of a field winding. Resin permanent magnets which are molded onto the ring are disposed between the field core claws so as to abut against the field core claws, respectively.
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Claims(5)
What is claimed is:
1. A rotor for an alternating current generator, comprising:
field core claws disposed on a field core;
a metal ring portion abutting against and holding said field core claws; and
resin permanent magnets being fixed to said metal ring portion and disposed between said field core claws;
wherein each of said resin permanent magnets abuts respective adjacent ones of said field core claws substantially without gaps therebetween.
2. The rotor according to claim 1, wherein a natural frequency of said metal ring portion is higher than that of said field core claws.
3. The rotor according to claim 1, wherein a coefficient of thermal expansion of said metal ring portion is greater than that of said field core claws.
4. The rotor according to claim 1,
wherein a rugged portion formed on one of a face of said metal ring portion and faces of said permanent magnets abuts said field core claws.
5. The rotor according to claim 1,
wherein said resin permanent magnets have faces with rugged portions that abut said field core claws.
Description
BACKGROUND OF THE INVENTION

The invention relates to an alternating current generator (hereinafter, referred to as AC generator) which is to be mounted on a vehicle or the like.

Generally, a technique is known in which, in an AC generator, permanent magnets are disposed between field core claws of a rotor so that magnetic fluxes are prevented from leaking, as disclosed in, for example, Unexamined Japanese patent publication (Kokai) 54-116610.

A technique in which, in order to prevent magnets from being separated from a rotor by a centrifugal caused by revolution of the rotor, a flange is extended from each magnet in the circumferential direction, or the magnets are formed into a substantially annular shape is disclosed in, for example, Unexamined Japanese patent publications (Kokai) 61-85045 and 4-49836.

Furthermore, a technique in which, in order to suppress wind noises generated by field core claws, a nonmagnetic ring is disposed at the same level as the outer peripheries of the field core claws is disclosed in, for example, Unexamined Japanese patent publication (Kokai) 3-265450.

In such conventional AC generators for a vehicle, however, a magnetic attraction force which changes in magnitude at a frequency proportional to the number of revolutions of a rotor is generated between a stator core and a field core or, more precisely, in small gaps between teeth of the stator core and field core claws. The components resonate at the fluctuation frequency of the magnetic attraction force, thereby generating noises which are called electromagnetic noises. According to the natural vibration mode (natural frequency) of the resonating component, the electromagnetic noises are classified into a low-speed electromagnetic noise which is generated at low-speed running mainly by resonation of the stator, and a high-speed electromagnetic noise which is generated at high-speed running mainly by resonation of the field core claws. Particularly, the high-speed electromagnetic noise which is caused when the rotor revolves at a high speed becomes a problem.

When a gap is formed between field core claws and permanent magnets disposed between the field core claws, the permanent magnets may move during revolution of the rotor to collide against the field core claws, with the result that the permanent magnets are broken.

SUMMARY OF THE INVENTION

The invention has been conducted in order to solve the above-discussed problems. It is an object of the invention to provide an alternating current generator which is low in noise level and excellent in efficiency.

It is another object of the invention to provide an alternating current generator which can be easily assembled and in which permanent magnets are surely fixed.

An alternating current generator of the invention comprises a rotor having a field core and a field winding, a stator opposing the rotor, and a plurality of field core claws disposed on the field core, the rotor being revolved by an external driving force, and further comprises a metal ring portion which is disposed so as to abut against and hold the field core claws, and resin permanent magnet portions which are fixed to the ring portion and disposed between the field core claws.

Further, an alternating current generator comprises a rotor having a field core and a field winding, a stator opposing the rotor, and a plurality of field core claws disposed on the field core, the rotor being revolved by an external driving force, and further comprises a holding member which holds permanent magnets disposed between the field core claws, and a rugged portion is formed on a face of the holding member or faces of the permanent magnet, the face or faces abutting against the field core claws.

Furthermore, an alternating-current generator comprises a rotor having a field core and a field winding, a stator opposing the rotor, and a plurality of field core claws disposed on the field core, the rotor being revolved by an external driving force, and further comprises resin permanent magnet portions which are disposed between the field core claws, and a rugged portion is formed on faces of the resin permanent magnets, the faces abutting against the field core claws.

The natural frequency of the ring portion is higher than at least the natural frequency of the field core claws.

The coefficient of thermal expansion of the ring portion is greater than at least the coefficient of thermal expansion of the field core claws.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing an AC generator for a vehicle according to Embodiment 1 of the invention;

FIG. 2 is a section view showing a rotor in Embodiment 1 of the invention;

FIG. 3 is a perspective view showing the rotor in Embodiment 1 of the invention;

FIG. 4 is a partial section view showing a holding member and field core claws in Embodiment 1 of the invention;

FIG. 5 is a perspective view showing the holding member in Embodiment 1 of the invention; and

FIG. 6 is a perspective view showing a stator in Embodiment 1 of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described.

FIG. 1 is a section view showing an AC generator for a vehicle according to Embodiment 1, FIG. 2 is a section view showing a rotor, FIG. 3 is a perspective view showing the rotor, FIG. 4 is a partial section view showing field core claws and a holding member of the rotor, FIG. 5 is a perspective view showing the holding member, and FIG. 6 is a perspective view showing a stator.

In the figures, 1 designates a rotor, 11 designates a rotating shaft which is driven by a driving force transmitted from an internal combustion engine of the vehicle (not shown) via a belt, and 12 designates a pair of roundel-type field cores which are made of steel and fitted onto the rotating shaft 11. Field core claws 12a are protruded from the field cores 12 and then bent in a substantially perpendicular manner so as to have the shape such as shown in FIG. 3. The reference numeral 13 designates a field winding, and 14 designates a winding bobbin. The pair of field cores 12 are disposed in such a manner that they oppose each other with the field winding 13 and the winding bobbin 14 therebetween and the field core claws 12a engage with each other.

A cooling fan 15 is fixedly attached by welding or the like to each of the side faces of the assembly of the field cores 12. The reference numeral 2 designates a stator which has a stator core 21 and a stator winding 22 as shown in FIG. 6. Stator core teeth 21a are formed on the surface of the stator core 21. The surface of the stator core 21 opposes the rotor 1 with being separated therefrom by a small gap. The reference numeral 3 designates a front bracket, and 4 designates a rear bracket. The rotor 1 is rotatably supported by the brackets via bearings 31 and 41. The stator 2 is sandwiched between the front and rear brackets 3 and 4.

The reference numeral 25 designates a holding member which is disposed between the engaging field core claws 12a and in a direction of the field winding 13. The holding member comprises an annular ring portion 25a which is made of steel and positioned between the field winding 13 and the field core claws 12a so as to serve as a base material of the holding member 25, and resin permanent magnet portions 25b each configured by a permanent magnet which is formed by solidifying a resin solution containing permanent magnet powder. The resin permanent magnet portions 25b are formed by molding so as to surround the ring portion 25a, and placed as shown in FIG. 3 so as to respectively fill the gaps between the field core claws 12a when the pair of field cores 12 are assembled.

As shown in FIG. 4, a rugged portion 25c is formed on each of faces 25d of the resin permanent magnet portions 25b which abut against the side faces 12b of the field core claws 12a, by forming a plurality of grooves when the permanent magnet portions are molded. When the field cores are to be assembled, the rugged portions 25c abut against the respective side faces 12b of the field core claws 12a, whereby dimensional errors of the field core claws 12a and variations in assembly are absorbed so as not to form a gap between the side faces 12b of the field core claws 12a and the resin permanent magnet portions 25b. After assembling, the rugged portions 25c of the resin permanent magnet portions 25b are pressed in both lateral directions by the field core claws 12a so that fixation is surely conducted.

Since the resin permanent magnet portions 25b are disposed in the gaps between the field core claws 12a, wind noises which are generated by the field core claws 12a during revolution of the rotor 1 is reduced in level.

In the rugged portions 25c, as shown in FIGS. 4 and 5, the grooves are formed in parallel with the axial direction of the rotating shaft 11. Alternatively, the grooves may be formed in a direction perpendicular to the rotating shaft 11, or at random. The rugged portions 25c may have a shape in which a plurality of substantially hemispherical protrusions are formed.

The ring portion 25a abuts against the inner sides of the field core claws 12a so as to hold the claws 12a. The field core claws 12a are protruded from the body of the field cores 12 and then bent. According to this shape, the natural frequency of the field core claws 12a is lower than that of the body of the field cores 12 so that the field core claws 12a resonate at the fluctuation frequency of the magnetic attraction force. In order to prevent this phenomenon from occurring, the ring portion 25a holds the field core claws 12a so as to improve the rigidity of the field core claws 12a themselves, thereby changing the natural frequency of the field core claws 12a. This prevents the field core claws 12a from resonating at the fluctuation frequency of the magnetic attraction force which is generated during the use of the AC generator.

In the embodiment, the natural frequency of the field core claws 12a is raised by holding them by the ring portion 25a, and hence the field core claws 12a do not resonate at the fluctuation frequency of the magnetic attraction force which may be generated in the usual use range. In this way, resonation of the field core claws 12a is suppressed by disposing the ring portion 25a, thereby preventing the field core claws 12a from generating noises.

As described above, the ring portion 25a holds the field core claws 12a while abutting against the claws, thereby raising the natural frequency of the field core claws 12a. When the ring portion 25a is greater in rigidity or higher in natural frequency than the field core claws 12a, it is possible to raise more surely the natural frequency of the field core claws 12a, and hence noises are prevented more surely from being generated.

When the ring portion 25a is increased in rigidity and formed into, for example, a strip-like shape, the area of the portions where the ring portion 25a abuts against the field core claws 12a can be increased. This can cause the field core claws 12a to resonate more hardly.

In the embodiment, the ring portion 25a and the field core claws 12a are made of steel. The materials may be selected so that the coefficient of thermal expansion of the ring portion 25a is greater than that of the field core claws 12a. In this case, when heat is generated during operation of the AC generator and the portion and claws are thermally expanded, the ring portion 25a further presses the field core claws 12a so that fixation is more surely conducted and the natural frequency of the field core claws 12a is raised.

Since the ring portion 25a can have a simple shape such as an annular shape, it can be easily produced. After the ring portion 25a is formed, the field core claws 12a can be formed by molding so as to partly surround the ring portion 25a. Even when the field core claws 12a and the rugged portions 25c have a complex shape, therefore, they can be easily produced.

Next, the operation will be described.

In the thus configured AC generator for a vehicle, a current is supplied from a battery which is not shown to the field winding 13 to generate a magnetic field, and the rotor 1 is caused to revolve by a driving force transmitted via a belt which is not shown, whereby a rotating magnetic field is generated in the vicinity of the rotor 1. A current is generated by the rotating magnetic field in the stator winding 22 of the stator core 21 which is separated from the rotor 1 by the small gap. When a current flows through the field winding 13, magnetism of N-pole or S-pole appears in each of the field core claws 12a so that magnetic fluxes are generated between the field core claws 12a of N-pole and those of S-pole. The resin permanent magnet portions 25b are previously magnetized in a direction along which leakage fluxes among the magnetic fluxes are prevented. As a result, leakage fluxes which pass through the resin permanent magnet portions 25b are reduced and field fluxes which intersect the stator winding 22 are increased so that the generator efficiency is improved.

Next, the assembly of the rotor 1 will be described.

First, the holding member 25 is placed so as to abut against one of the paired field cores 12. At this time, also the field winding 13 and the winding bobbin 14 are placed. Thereafter, the other field core 12 is placed in such a manner that the holding member 25 is sandwiched by the field cores and the field core claws 12a alternately engage with each other.

At this time, the side faces 12b of the field core claws 12a abut against the side faces 25d of the resin permanent magnet portions 25b, respectively. Therefore, the protrusions of the rugged portions 25c in the side faces 25d of the resin permanent magnet portions 25b are pressed by the side faces 12b of the field core claws 12a so as to be somewhat deformed, whereby dimensional errors of the components are eliminated.

In this Embodiment configured as described, wind noises generated by revolution can be reduced by disposing the resin permanent magnet portions 25b between the adjacent side faces 12b of the engaging field core claws 12a so that the rotor 1 is formed as a whole into a substantially cylindrical shape. The resin permanent magnet portions 25b prevent magnetic fluxes from leaking from the field core claws 12a.

In order to facilitate production, fixation, etc., as shown in FIG. 5, the holding member 25 is configured so as to have a strip-like shape, i.e., a rectangular or elliptic section shape. Alternatively, the holding member may have another shape as far as it can hold the field core claws 12a from the inner side. Furthermore, a rugged portion may be disposed in areas of the holding member onto which the resin permanent magnet portions 25b are to be molded, so that fixation after molding is ensured.

The resin permanent magnet portions 25b are made of a resin and are not integrated with the field core claws 12a, and hence it is possible to absorb dimensional errors. Since the resin permanent magnet portions 25b are integrated with the ring portion 25a made of steel, they are not broken even when subjected to a centrifugal force generated by revolution of the rotor 1 of the vehicle generator which can reach about 18,000 rpm.

In the Embodiment, the resin permanent magnets abut against the field core claws in order to reduce leakage fluxes. Alternatively, a solid permanent magnet may be covered with a resin or the like, and a rugged portion may be formed on the resin.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3230404 *Oct 10, 1961Jan 18, 1966Chrysler CorpDamping means for claw tooth rotors
US5306977 *Aug 7, 1992Apr 26, 1994Nippondenso Co., Ltd.Cooling rotor for an alternator mounted on vehicle
US5329199 *Nov 23, 1992Jul 12, 1994Ford Motor CompanyRotor assembly with molded fans and method for making the same
US5483166 *Apr 2, 1993Jan 9, 1996Olsen; Ib I.Electrochemical test cell for conductivity and transport measurements
US5519277 *Dec 27, 1994May 21, 1996Ford Motor CompanyRotor assembly for an electric machine
US5539265 *Oct 11, 1994Jul 23, 1996Ford Motor CompanySelf-aligning rotor assembly
US5578885 *Dec 22, 1994Nov 26, 1996General Motors CorporationRotor assembly for hybrid alternator
EP0188877A1 *Nov 19, 1985Jul 30, 1986General Motors CorporationAlternating current generator rotor
EP0394528B1 *Apr 27, 1989Jan 20, 1993Siemens AktiengesellschaftSynchronous machine
GB1560747A * Title not available
GB2111761A * Title not available
GB2281665A * Title not available
JPH0449836A * Title not available
JPH03265450A * Title not available
JPS6185045A * Title not available
JPS54116610A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5977668 *Feb 22, 1999Nov 2, 1999Mitsubishi Denki Kabushiki KaishaVehicle alternator and method of manufacture therefor
US6011343 *Mar 10, 1998Jan 4, 2000Denso CorporationRotor of rotary machine having claw poles and auxiliary permanent magnets
US6013967 *Jan 26, 1999Jan 11, 2000Robert Bosch GmbhSynchronous machine, in particular generator for motor vehicle
US6013968 *Jan 26, 1999Jan 11, 2000Robert Bosch GmbhSynchronous machine, in particular generator for motor vehicle
US6034464 *Dec 11, 1998Mar 7, 2000Mitsubishi Denki Kabushiki KaishaVehicle alternator
US6104118 *Mar 5, 1999Aug 15, 2000Hitachi, Ltd.Alternating current generator for use in vehicle
US6157111 *May 1, 1998Dec 5, 2000Mitsubishi Denki Kabushiki KaishaRotor for dynamo-electric machine
US6281612 *May 18, 1999Aug 28, 2001Mitsubishi Denki Kabushiki KaishaStator of AC generator for use in vehicle and method of manufacturing the same
US6307297May 5, 2000Oct 23, 2001Visteon Global Technologies, Inc.Recessed alternator pole piece
US6541890Jul 26, 2001Apr 1, 2003Denso CorporationBrush-less rotary electric machine having stator cooling arrangement
US6633096 *Oct 10, 2001Oct 14, 2003Denso CorporationAlternator
US6661151 *Nov 1, 2001Dec 9, 2003Denso CorporationAlternator for vehicles having permanent magnets in rotor
US6664695Apr 16, 2001Dec 16, 2003Mitsubishi Denki Kabushiki KaishaStator of AC generator for use in a vehicle with radially aligned, rectilinear polymorphic cross-section conductor wires
US6744165 *Oct 29, 2002Jun 1, 2004Visteon Global Technologies, Inc.High power permanent magnet hybrid alternator rotor
US6784577 *May 8, 2002Aug 31, 2004Denso CorporationVehicular AC current generator rotor having field-coil winding finishing-end hook portions
US6806616 *Oct 28, 2003Oct 19, 2004Mitsubishi Denki Kabushiki KaishaRotor of rotating electric machine
US6833651 *Oct 23, 2002Dec 21, 2004Robert Bosch GmbhClaw-pole rotor and production method therefor
US6900570 *Dec 1, 2000May 31, 2005Ecoair Corp.Field controlled permanent magnet brushless electric machine
US7057327 *Aug 30, 2001Jun 6, 2006Hitachi, Ltd.Vehicular alternator
US7800261 *Jul 17, 2006Sep 21, 2010Denso CorporationRotary electric machine with stator outer surface designed to enhance heat dissipation
US8283833Oct 9, 2012Denso CorporationRotor for electric rotary machine
US20020167233 *May 8, 2002Nov 14, 2002Denso CorporationRotor for vehicular alternating current generator
US20020180297 *Dec 1, 2000Dec 5, 2002Costin IfrimHybrid brushless electric machine
US20040036376 *Oct 23, 2002Feb 26, 2004Gerhard PfluegerClaw-pole rotor and production mehod therefor
US20040135464 *Oct 28, 2003Jul 15, 2004Mitsubishi Denki Kabushiki KaishaRotor of rotating electric machine
US20070013259 *Jul 17, 2006Jan 18, 2007Denso CorporationRotary electric machine with stator outer surface designed to enhance heat dissipation
CN102150343B *May 26, 2009Nov 25, 2015法雷奥电机设备公司用于旋转电机的具有质量减小的极间结构的转子
DE10153578B4 *Oct 31, 2001Jan 26, 2012Denso CorporationWechselstromgenerator für Fahrzeuge mit Permanentmagneten im Rotor und Verfahren zur Herstellung desselben
DE10318636B4 *Apr 24, 2003Nov 20, 2014Hitachi, Ltd.Rotor für eine Wechselstromlichtmaschine für den Einsatz in Fahrzeugen
DE102007034326A1 *Jul 24, 2007Jan 29, 2009Robert Bosch GmbhElektrische Maschine
EP1176699A1 *Jul 23, 2001Jan 30, 2002Denso CorporationBrush-less rotary electric machine having stator cooling arrangement
WO2001042649A2 *Dec 1, 2000Jun 14, 2001Ecoair Corp.Hybrid brushless electric machine
WO2001042649A3 *Dec 1, 2000Feb 21, 2002Ecoair CorpHybrid brushless electric machine
WO2007147922A1 *Jun 12, 2007Dec 27, 2007Gamesa Innovation & Technology, S.L.Low-inertia permanent-magnet electrical machine rotor.
Classifications
U.S. Classification310/263, 310/181
International ClassificationH02K19/22, H02K1/24, H02K1/22, H02K1/27
Cooperative ClassificationH02K21/044, H02K1/243
European ClassificationH02K21/04R1, H02K1/24B
Legal Events
DateCodeEventDescription
Jun 5, 1996ASAssignment
Owner name: MITSUBISHI DENKI KABUSHIKI KAISHA, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ADACHI, KATSUMI;KURUSU, KYOKO;REEL/FRAME:008036/0980
Effective date: 19960529
Apr 4, 2002FPAYFee payment
Year of fee payment: 4
Mar 31, 2006FPAYFee payment
Year of fee payment: 8
Apr 21, 2010FPAYFee payment
Year of fee payment: 12